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Researchers from the University of Queensland and the University of New South Wales found that eye color could be an indicator of how agreeable a person is. The researchers found that Northern Europeans with lighter-colored eyes tended to be less agreeable and more competitive than their peers.

The study was conducted in Australia. Researchers conducted a study among 336 participants, 63 percent of whom were Northern European in ancestry. Study participants were asked to report their eye color, as well as answer a series of questionnaires that measured aspects of their personalities, like agreeableness, conscientiousness and neuroticism.

Researchers found that people with darker eyes were seen as more agreeable. Northern Europeans with lighter eyes were seen as more competitive, egocentric and skeptical of others, while Northern Europeans with darker eyes were seen as more altruistic, sympathetic and willing to help others. Researchers did not find that the same correlation existed for other Europeans.

While the connection between personality and eye color may seem strange and weak, researchers believe that the link has evolutionary roots.

Thousands of years ago, the cold, dry climate of the last Ice Age in northern Europe forced a shortage of food. Men needed to travel long distances in order to obtain food, causing them to die off at higher rates than women did. Theories suggest that competition for care by men was fierce for women, and that both men and women with rarer, lighter eye colors had an easier time attracting mates.

The research is an expansion of other studies conducted on eye color, personality and genetic traits. Previous research has shown that eye color is an indicator of alcohol abuse, response styles and sociability.